WO2021173463A1 - Semiconductor device including a superlattice with different non-semiconductor material monolayers and associated methods - Google Patents
Semiconductor device including a superlattice with different non-semiconductor material monolayers and associated methods Download PDFInfo
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- WO2021173463A1 WO2021173463A1 PCT/US2021/018972 US2021018972W WO2021173463A1 WO 2021173463 A1 WO2021173463 A1 WO 2021173463A1 US 2021018972 W US2021018972 W US 2021018972W WO 2021173463 A1 WO2021173463 A1 WO 2021173463A1
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/02—Semiconductor bodies ; Multistep manufacturing processes therefor
- H01L29/12—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed
- H01L29/15—Structures with periodic or quasi periodic potential variation, e.g. multiple quantum wells, superlattices
- H01L29/151—Compositional structures
Definitions
- SEMICONDUCTOR DEVICE INCLUDING A SUPERLATTICE WITH DIFFERENT NON-SEMICONDUCTOR MATERIAL MONOLAYERS AND ASSOCIATED
- the present disclosure generally relates to semiconductor devices and, more particularly, to semiconductor devices with enhanced semiconductor materials and related methods.
- U.S. Patent No. 6,472,685 B2 to Takagi discloses a semiconductor device including a silicon and carbon layer sandwiched between silicon layers so that the conduction band and valence band of the second silicon layer receive a tensile strain. Electrons having a smaller effective mass, and which have been induced by an electric field applied to the gate electrode, are confined in the second silicon layer, thus, an n-channel MOSFET is asserted to have a higher mobility.
- a superlattice in which a plurality of layers, less than eight monolayers, and containing a fractional or binary or a binary compound semiconductor layer, are alternately and epitaxially grown.
- the direction of main current flow is perpendicular to the layers of the superlattice.
- U.S. Patent No. 5,357,119 to Wang et al. discloses a Si-Ge short period superlattice with higher mobility achieved by reducing alloy scattering in the superlattice.
- U.S. Patent No. 5,683,934 to Candelaria discloses an enhanced mobility MOSFET including a channel layer comprising an alloy of silicon and a second material substitutionally present in the silicon lattice at a percentage that places the channel layer under tensile stress.
- U.S. Patent No. 5,216,262 to Tsu discloses a quantum well structure comprising two barrier regions and a thin epitaxially grown semiconductor layer sandwiched between the barriers.
- Each barrier region consists of alternate layers of Si02/Si with a thickness generally in a range of two to six monolayers. A much thicker section of silicon is sandwiched between the barriers.
- An article entitled “Phenomena in silicon nanostructure devices” also to Tsu and published online September 6, 2000 by Applied Physics and Materials Science & Processing, pp. 391-402 discloses a semiconductor-atomic superlattice (SAS) of silicon and oxygen.
- the Si/O superlattice is disclosed as useful in a silicon quantum and light-emitting devices.
- a green electroluminescence diode structure was constructed and tested. Current flow in the diode structure is vertical, that is, perpendicular to the layers of the SAS.
- the disclosed SAS may include semiconductor layers separated by adsorbed species such as oxygen atoms, and CO molecules. The silicon growth beyond the adsorbed monolayer of oxygen is described as epitaxial with a fairly low defect density.
- One SAS structure included a 1.1 nm thick silicon portion that is about eight atomic layers of silicon, and another structure had twice this thickness of silicon.
- An article to Luo et al. entitled “Chemical Design of Direct-Gap Light-Emitting Silicon” published in Physical Review Letters, Vol. 89, No. 7 (August 12, 2002) further discusses the light emitting SAS structures of Tsu.
- U.S. Pat. No. 7,105,895 to Wang et al. discloses a barrier building block of thin silicon and oxygen, carbon, nitrogen, phosphorous, antimony, arsenic or hydrogen to thereby reduce current flowing vertically through the lattice more than four orders of magnitude.
- the insulating layer/barrier layer allows for low defect epitaxial silicon to be deposited next to the insulating layer.
- U.S. Pat. No. 6,376,337 to Wang et al. discloses a method for producing an insulating or barrier layer for semiconductor devices which includes depositing a layer of silicon and at least one additional element on the silicon substrate whereby the deposited layer is substantially free of defects such that epitaxial silicon substantially free of defects can be deposited on the deposited layer.
- a monolayer of one or more elements, preferably comprising oxygen, is absorbed on a silicon substrate.
- a plurality of insulating layers sandwiched between epitaxial silicon forms a barrier composite.
- a semiconductor device may include a semiconductor substrate, and a superlattice on the semiconductor substrate and including a plurality of stacked groups of layers.
- Each group of layers of the superlattice may include a plurality of stacked base semiconductor monolayers defining a base semiconductor portion and at least one non-semiconductor monolayer constrained within a crystal lattice of adjacent base semiconductor portions.
- a first at least one non-semiconductor monolayer may be constrained within the crystal lattice of a first pair of adjacent base semiconductor portions and comprise a first non-semiconductor material
- a second at least one non-semiconductor monolayer may be constrained within the crystal lattice of a second pair of adjacent base semiconductor portions and comprise a second non-semiconductor material different than the first non semiconductor material.
- the first non-semiconductor material may comprise oxygen and nitrogen
- the second non-semiconductor material may comprise at least one of carbon and oxygen.
- a third at least one non-semiconductor monolayer may be constrained within the crystal lattice of a third pair of adjacent base semiconductor portions and comprise a third non semiconductor material different than the first and second non-semiconductor materials.
- the first non-semiconductor material may comprise nitrogen, and the first at least one non-semiconductor monolayer may be above the second at least one non-semiconductor monolayer in the superlattice.
- a base semiconductor portion between the first at least one non-semiconductor monolayer and the second at least one non semiconductor monolayer may comprise a carbon dopant.
- the base semiconductor monolayers may comprise silicon, for example.
- the semiconductor device may further include spaced apart source and drain regions defining a channel within the superlattice, and a gate overlying the channel.
- a method for making a semiconductor device may include forming a superlattice on a semiconductor substrate and including a plurality of stacked groups of layers.
- Each group of layers of the superlattice may include a plurality of stacked base semiconductor monolayers defining a base semiconductor portion and at least one non-semiconductor monolayer constrained within a crystal lattice of adjacent base semiconductor portions.
- a first at least one non-semiconductor monolayer may be constrained within the crystal lattice of a first pair of adjacent base semiconductor portions and comprise a first non-semiconductor material
- a second at least one non-semiconductor monolayer may be constrained within the crystal lattice of a second pair of adjacent base semiconductor portions and comprise a second non semiconductor material different than the first non-semiconductor material.
- the first non-semiconductor material may comprise oxygen and nitrogen
- the second non-semiconductor material may comprise at least one of carbon and oxygen.
- a third at least one non-semiconductor monolayer may be constrained within the crystal lattice of a third pair of adjacent base semiconductor portions comprising a third non-semiconductor material different than the first and second non-semiconductor materials.
- the first non-semiconductor material may comprise nitrogen, and the first at least one non-semiconductor monolayer may be above the second at least one non-semiconductor monolayer in the superlattice.
- a base semiconductor portion between the first at least one non-semiconductor monolayer and the second at least one non semiconductor monolayer may comprise a carbon dopant.
- the base semiconductor monolayers may comprise silicon, for example.
- the method may further include forming spaced apart source and drain regions defining a channel within the superlattice, and a gate overlying the channel.
- FIG. 1 is a greatly enlarged schematic cross-sectional view of a superlattice for use in a semiconductor device in accordance with an example embodiment.
- FIG. 2 is a perspective schematic atomic diagram of a portion of the superlattice shown in FIG. 1.
- FIG. 3 is a greatly enlarged schematic cross-sectional view of another embodiment of a superlattice in accordance with an example embodiment.
- FIG. 4A is a graph of the calculated band structure from the gamma point (G) for both bulk silicon as in the prior art, and for the 4/1 Si/O superlattice as shown in FIGS. 1-2.
- FIG. 4B is a graph of the calculated band structure from the Z point for both bulk silicon as in the prior art, and for the 4/1 Si/O superlattice as shown in FIGS. 1-2.
- FIG. 4C is a graph of the calculated band structure from both the gamma and Z points for both bulk silicon as in the prior art, and for the 5/1 /3/1 Si/O superlattice as shown in FIG. 3.
- FIGS. 5-9 are schematic cross-sectional diagrams of different example embodiments of superlattices having different non-semiconductor material layers therein.
- FIG. 10 is a flow diagram illustrating a method of making a semiconductor device including any of the superlattices of FIGS. 5-9 in accordance with an example embodiment.
- FIG. 11 is a schematic cross-sectional diagram of an example semiconductor device which may be fabricated in accordance with the method of FIG. 10.
- the present disclosure relates to utilizing enhanced superlattice materials within source and drain regions to reduce Schottky barrier height and thereby decrease source and drain contact resistance.
- the enhanced semiconductor superlattice is also referred to as an “MST” layer or “MST technology” in this disclosure and the accompanying drawings.
- the MST technology relates to advanced semiconductor materials such as the superlattice 25 described further below.
- Applicant theorizes, without wishing to be bound thereto, that certain superlattices as described herein reduce the effective mass of charge carriers and that this thereby leads to higher charge carrier mobility. Effective mass is described with various definitions in the literature. As a measure of the improvement in effective mass
- Applicants use a "conductivity reciprocal effective mass tensor", e and M h for electrons and holes respectively, defined as: for electrons and: for holes, where is the Fermi-Dirac distribution, EF is the Fermi energy, T is the temperature, E(k,n) is the energy of an electron in the state corresponding to wave vector k and the n th energy band, the indices i and j refer to Cartesian coordinates x, y and z, the integrals are taken over the Brillouin zone (B.Z.), and the summations are taken over bands with energies above and below the Fermi energy for electrons and holes respectively.
- e and M h for electrons and holes respectively, defined as: for electrons and: for holes, where is the Fermi-Dirac distribution, EF is the Fermi energy, T is the temperature, E(k,n) is the energy of an electron in the state corresponding to wave vector k and the n th energy band, the
- Applicant s definition of the conductivity reciprocal effective mass tensor is such that a tensorial component of the conductivity of the material is greater for greater values of the corresponding component of the conductivity reciprocal effective mass tensor.
- Applicant theorizes without wishing to be bound thereto that the superlattices described herein set the values of the conductivity reciprocal effective mass tensor so as to enhance the conductive properties of the material, such as typically for a preferred direction of charge carrier transport.
- the inverse of the appropriate tensor element is referred to as the conductivity effective mass.
- the conductivity effective mass for electrons/holes as described above and calculated in the direction of intended carrier transport is used to distinguish improved materials.
- Applicant has identified improved materials or structures for use in semiconductor devices. More specifically, Applicant has identified materials or structures having energy band structures for which the appropriate conductivity effective masses for electrons and/or holes are substantially less than the corresponding values for silicon. In addition to the enhanced mobility characteristics of these structures, they may also be formed or used in such a manner that they provide piezoelectric, pyroelectric, and/or ferroelectric properties that are advantageous for use in a variety of different types of devices, as will be discussed further below.
- the materials or structures are in the form of a superlattice 25 whose structure is controlled at the atomic or molecular level and may be formed using known techniques of atomic or molecular layer deposition.
- the superlattice 25 includes a plurality of layer groups 45a-45n arranged in stacked relation, as perhaps best understood with specific reference to the schematic cross-sectional view of FIG. 1.
- Each group of layers 45a-45n of the superlattice 25 illustratively includes a plurality of stacked base semiconductor monolayers 46 defining a respective base semiconductor portion 46a-46n and an energy band-modifying layer 50 thereon.
- the energy band-modifying layers 50 are indicated by stippling in FIG. 1 for clarity of illustration.
- the energy band-modifying layer 50 illustratively includes one non semiconductor monolayer constrained within a crystal lattice of adjacent base semiconductor portions. By “constrained within a crystal lattice of adjacent base semiconductor portions” it is meant that at least some semiconductor atoms from opposing base semiconductor portions 46a-46n are chemically bound together through the non-semiconductor monolayer 50 therebetween, as seen in FIG. 2.
- this configuration is made possible by controlling the amount of non-semiconductor material that is deposited on semiconductor portions 46a-46n through atomic layer deposition techniques so that not all (i.e. , less than full or 100% coverage) of the available semiconductor bonding sites are populated with bonds to non-semiconductor atoms, as will be discussed further below.
- the newly deposited semiconductor atoms will populate the remaining vacant bonding sites of the semiconductor atoms below the non-semiconductor monolayer.
- non-semiconductor monolayer may be possible.
- reference herein to a non semiconductor or semiconductor monolayer means that the material used for the monolayer would be a non-semiconductor or semiconductor if formed in bulk. That is, a single monolayer of a material, such as silicon, may not necessarily exhibit the same properties that it would if formed in bulk or in a relatively thick layer, as will be appreciated by those skilled in the art.
- this superlattice structure may also advantageously act as a barrier to dopant and/or material diffusion between layers vertically above and below the superlattice 25. These properties may thus advantageously allow the superlattice 25 to provide an interface for high-K dielectrics which not only reduces diffusion of the high-K material into the channel region, but which may also advantageously reduce unwanted scattering effects and improve device mobility, as will be appreciated by those skilled in the art.
- the superlattice 25 may enjoy a higher charge carrier mobility based upon the lower conductivity effective mass than would otherwise be present.
- the superlattice 25 may further have a substantially direct energy bandgap that may be particularly advantageous for opto-electronic devices, for example.
- the superlattice 25 also illustratively includes a cap layer 52 on an upper layer group 45n.
- the cap layer 52 may comprise a plurality of base semiconductor monolayers 46.
- the cap layer 52 may have between 2 to 100 monolayers of the base semiconductor, and, more preferably between 10 to 50 monolayers.
- Each base semiconductor portion 46a-46n may comprise a base semiconductor selected from the group consisting of Group IV semiconductors, Group lll-V semiconductors, and Group ll-VI semiconductors.
- Group IV semiconductors also includes Group IV-IV semiconductors, as will be appreciated by those skilled in the art.
- the base semiconductor may comprise at least one of silicon and germanium, for example.
- Each energy band-modifying layer 50 may comprise a non semiconductor selected from the group consisting of oxygen, nitrogen, fluorine, carbon and carbon-oxygen, for example.
- the non-semiconductor is also desirably thermally stable through deposition of a next layer to thereby facilitate manufacturing.
- the non-semiconductor may be another inorganic or organic element or compound that is compatible with the given semiconductor processing as will be appreciated by those skilled in the art.
- the base semiconductor may comprise at least one of silicon and germanium, for example.
- the term monolayer is meant to include a single atomic layer and also a single molecular layer.
- the energy band modifying layer 50 provided by a single monolayer is also meant to include a monolayer wherein not all of the possible sites are occupied (i.e. , there is less than full or 100% coverage).
- a 4/1 repeating structure is illustrated for silicon as the base semiconductor material, and oxygen as the energy band-modifying material. Only half of the possible sites for oxygen are occupied in the illustrated example.
- this one-half occupation would not necessarily be the case as will be appreciated by those skilled in the art. Indeed, it can be seen even in this schematic diagram, that individual atoms of oxygen in a given monolayer are not precisely aligned along a flat plane as will also be appreciated by those of skill in the art of atomic deposition.
- a preferred occupation range is from about one-eighth to one-half of the possible oxygen sites being full, although other numbers may be used in certain embodiments.
- the number of silicon monolayers should desirably be seven or less so that the energy band of the superlattice is common or relatively uniform throughout to achieve the desired advantages.
- the 4/1 repeating structure shown in FIGS. 1 and 2, for Si/O has been modeled to indicate an enhanced mobility for electrons and holes in the X direction.
- the calculated conductivity effective mass for electrons is 0.26
- the 4/1 SiO superlattice in the X direction it is 0.12 resulting in a ratio of 0.46.
- the calculation for holes yields values of 0.36 for bulk silicon and 0.16 for the 4/1 Si/O superlattice resulting in a ratio of 0.44.
- the lower conductivity effective mass for the 4/1 Si/O embodiment of the superlattice 25 may be less than two-thirds the conductivity effective mass than would otherwise occur, and this applies for both electrons and holes.
- the superlattice 25 may further comprise at least one type of conductivity dopant therein, as will also be appreciated by those skilled in the art.
- FIG. 3 another embodiment of a superlattice 25’ in accordance with the invention having different properties is now described.
- a repeating pattern of 3/1/5/1 is illustrated. More particularly, the lowest base semiconductor portion 46a’ has three monolayers, and the second lowest base semiconductor portion 46b’ has five monolayers. This pattern repeats throughout the superlattice 25’.
- the energy band-modifying layers 50’ may each include a single monolayer.
- the enhancement of charge carrier mobility is independent of orientation in the plane of the layers.
- all of the base semiconductor portions of a superlattice may be a same number of monolayers thick. In other embodiments, at least some of the base semiconductor portions may be a different number of monolayers thick. In still other embodiments, all of the base semiconductor portions may be a different number of monolayers thick.
- FIGS. 4A-4C band structures calculated using Density Functional Theory (DFT) are presented. It is well known in the art that DFT underestimates the absolute value of the bandgap. Flence all bands above the gap may be shifted by an appropriate “scissors correction.” Flowever, the shape of the band is known to be much more reliable. The vertical energy axes should be interpreted in this light.
- FIG. 4A shows the calculated band structure from the gamma point (G) for both bulk silicon (represented by continuous lines) and for the 4/1 Si/O superlattice 25 shown in FIG. 1 (represented by dotted lines).
- the directions refer to the unit cell of the 4/1 Si/O structure and not to the conventional unit cell of Si, although the (001) direction in the figure does correspond to the (001) direction of the conventional unit cell of Si, and, hence, shows the expected location of the Si conduction band minimum.
- the (100) and (010) directions in the figure correspond to the (110) and (-110) directions of the conventional Si unit cell.
- the bands of Si on the figure are folded to represent them on the appropriate reciprocal lattice directions for the 4/1 Si/O structure.
- the conduction band minimum for the 4/1 Si/O structure is located at the gamma point in contrast to bulk silicon (Si), whereas the valence band minimum occurs at the edge of the Brillouin zone in the (001) direction which we refer to as the Z point.
- the greater curvature of the conduction band minimum for the 4/1 Si/O structure compared to the curvature of the conduction band minimum for Si owing to the band splitting due to the perturbation introduced by the additional oxygen layer.
- FIG. 4B shows the calculated band structure from the Z point for both bulk silicon (continuous lines) and for the 4/1 Si/O superlattice 25 (dotted lines). This figure illustrates the enhanced curvature of the valence band in the (100) direction.
- FIG. 4C shows the calculated band structure from both the gamma and Z point for both bulk silicon (continuous lines) and for the 5/1 /3/1 Si/O structure of the superlattice 25’ of FIG. 3 (dotted lines). Due to the symmetry of the 5/1 /3/1 Si/O structure, the calculated band structures in the (100) and (010) directions are equivalent. Thus, the conductivity effective mass and mobility are expected to be isotropic in the plane parallel to the layers, i.e. perpendicular to the (001) stacking direction. Note that in the 5/1/3/1 Si/O example the conduction band minimum and the valence band maximum are both at or close to the Z point.
- FIGS. 5-9 other example superlattice structures are now described which incorporate different types of non-semiconductor materials in different non-semiconductor monolayers 50.
- co-pending U.S. app. no. 16/176,005 to Weeks et al. (which is assigned to the present Applicant and is hereby incorporated herein in its entirety by reference) teaches an approach for using the above-described MST material as a nitrogen gettering layer. By diffusing nitrogen into the MST film monolayers after epitaxial deposition, this allows for a greater final dosage of nitrogen to boost dopant blocking and mobility enhancement, for example.
- the nitrogen infused into the MST gettering layer may penetrate all of the non-semiconductor monolayers 50, which in the case of an Si/O superlattice would mean that each of the non semiconductor monolayers would include both oxygen and nitrogen.
- a superlattice 125 is formed on a semiconductor (e.g., silicon) substrate 121 (which may be patterned or unpatterned), and the superlattice illustratively includes in stacked order an oxygen monolayer(s) 150a, a base silicon portion 146a including a carbon dopant, another oxygen monolayer(s) 150b, a base silicon portion 146b without a carbon dopant, another oxygen monolayer(s) 150c, and another base silicon portion 146c including a carbon dopant.
- the carbon in the base silicon portion 146c advantageously helps block or shield nitrogen 53 from diffusing down into the monolayers 150a-150c.
- the nitrogen 153 is blocked from the lower oxygen monolayers 150a-150c by the carbon in the base silicon portions 146c. This results in most or all of the nitrogen being trapped in the upper MST spacers and inserted MST oxygen layers.
- the total absorbed nitrogen will be equal to the total amount that would have been evenly distributed over the full superlattice 125 stack without the carbon shielding.
- the next three non-semiconductor monolayers 150d-150f in the stack include oxygen and nitrogen.
- a silicon cap layer 152 is formed on the upper non semiconductor layer 150f, and is terminated in a nitride (SiN) layer 154.
- the illustrated example includes six non-semiconductor monolayers 150a-150f (with three above the final carbon-infused silicon base portion 146c), in which the carbon also helps stabilize/block the oxygen from being lost, although different numbers of semiconductor base portions and non-semiconductor monolayers may be used in different embodiments.
- a greater number of oxygen monolayers may be included bellow the carbon.
- the result would be that the total nitrogen 153’ drawn from the surface would all pile up in the top most oxygen monolayers above the carbon. This could be used to form a silicon oxynitride layer or greater quantum mechanical manipulation, depending on the degree of nitrogen 153’ piled up in the upper carbon-free base silicon portions, as will be appreciated by those skilled in the art.
- FIG. 7 includes a substrate 221, non semiconductor (e.g., oxygen) monolayers 250a-250f, base semiconductor (e.g., silicon) portions 246a-246e, a semiconductor (e.g., silicon) cap layer 252, and nitride (e.g., SiN) layer 254, similar to the embodiments discussed above.
- base semiconductor e.g., silicon
- nitride e.g., SiN
- carbon may be co-dosed, dosed after the oxygen, or before the oxygen in different embodiments.
- the carbon used to block the nitrogen 253 from diffusing into the lower oxygen monolayers 250a, 250b resides with the oxygen in the monolayer(s) 250c instead of with any of the silicon base portions 246a-246e.
- the present example illustrates just the middle oxygen monolayer(s) 250c having carbon, but in different embodiments other oxygen monolayers may have carbon as well to provide for even greater confinement of the nitrogen 253 to the upper two oxygen monolayers 250e, 250f and base silicon portions 246d, 246e.
- all or substantially all of the dose of nitrogen 253 that would have otherwise been distributed over the six oxygen monolayers 250a-250f may instead be confined to the upper two oxygen monolayers 250e, 250f.
- One such example superlattice 225’ is illustrated in FIG. 8, in which all three of the bottom oxygen monolayers 250a’-250c’ have carbon atoms inserted therein.
- the superlattice 325 includes a substrate 321, non-semiconductor (e.g., oxygen) monolayers 350a-350f, base semiconductor (e.g., silicon) portions 346a-346e, a semiconductor (e.g., silicon) cap layer 352, and nitride (e.g., SiN) layer 354, similar to the embodiments discussed above.
- non-semiconductor e.g., oxygen
- base semiconductor e.g., silicon
- a semiconductor e.g., silicon
- nitride e.g., SiN
- all of the lower oxygen monolayers 350a-350d and base silicon portions 346a-346c have carbon added for greater confinement of the nitrogen 353 to the upper two oxygen monolayers 350e, 350f and base silicon layers 346d, 346e.
- an MST superlattice module may be performed (Block 402) to form the basic MST structure on a semiconductor substrate 421 with a blocking material (such as carbon) implanted or deposited within one or more of the base semiconductor (e.g., silicon) portions and/or the non semiconductor (e.g., oxygen) monolayers, as discussed above.
- a blocking material such as carbon
- the base semiconductor e.g., silicon
- the non semiconductor e.g., oxygen
- the carbon may be on the order of a 1 E15 atoms/cm 2 dose per insert (or less), and more particularly around 2.5E14 atoms/cm 2 per insert, for example.
- the concentration may be between 0.01 to 10 atomic percent, and more particularly between 0.1 and 2 atomic percent carbon in each base silicon portion, for example.
- the carbon source gas may be added with the silicon precursors during the chemical vapor deposition process of the base silicon layers.
- Example gaseous carbon sources include propene (propylene C3H6), cyclopropane (C3H6), and methyl-silane (SiFhCFh), for example.
- Another approach is to implant carbon into just the lower base silicon portions, and have the upper base silicon portions without the carbon dose.
- the semiconductor device 420 which in the present example is a planar MOSFET.
- the illustrated MOSFET 420 includes the substrate 421, source/drain regions 422, 423, source/drain extensions 426, 427, and a channel region therebetween provided by the superlattice 425.
- Source/drain silicide layers 430, 431 and source/drain contacts 432, 433 overlie the source/drain regions, as will be appreciated by those skilled in the art.
- Regions indicated by dashed lines 434, 435 are optional vestigial portions formed originally with the superlattice 425, but thereafter heavily doped. In other embodiments, these vestigial superlattice regions 434, 435 may not be present as will also be appreciated by those skilled in the art.
- a gate 435 illustratively includes a gate insulating layer 437 adjacent the channel provided by the superlattice 425, and a gate electrode layer 436 on the gate insulating layer. Sidewall spacers 440, 441 are also provided in the illustrated MOSFET 420.
- the present approach utilizes carbon for blocking/isolating some or all of the nitrogen dose to the upper unblocked inserted oxygen monolayers. This may advantageously increase the total nitrogen content in the upper unblocked superlattice layers. For example, it has been demonstrated that a seven-layer MST superlattice stack with 1.58E15 atoms/cm 2 creates enough of a driving force to attract 0.5E15 atoms/cm 2 nitrogen during a 900°C N2 anneal.
- the localized enhancement may be greater due to the nitrogen right near the surface being higher.
- SOI silicon-on-isolator
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US16/801,305 US11177351B2 (en) | 2020-02-26 | 2020-02-26 | Semiconductor device including a superlattice with different non-semiconductor material monolayers |
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TW202133438A (zh) | 2021-09-01 |
EP4111504A1 (en) | 2023-01-04 |
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